ESPE Abstracts

Background: Preterm newborns due to their immaturity, a higher incidence of mortality and increased susceptibility to iodine, are at risk of decreased thyroid function. Low levels of thyroid hormones during a critical period for the development of the central nervous system may negatively affect their psychomotor development. Screening for congenital hypothyroidism with capillary TSH is invalid for preterm babies and would require an specific thyroid function control.

Objective and hypotheses: To assess the protocol applied in our hospital during 2011–2014. To find out the prevalence of hypothyroxinaemia and hyperthyrotropinemia of prematurity. To review how many premature are treated and its clinical evolution.

Method: Longitudinal descriptive and prospective study of thyroid function in preterm infants admitted to NICU during 2011 2014. Determination of FT4 and TSH (venous sample blood test) in the 2nd week of life, depending on the results:• If TSH 5–15 mU/L and: fT₄ <0.8 ng/dl repeat in 24–48 h *;- fT₄ >0.8 ng/dl repeat in 10–15 days; – fT₄ >1 ng/dl repeat in 4 weeks or before discharge. • If TSH>12–15 mU/L, in two determinations initiate levothyroxine. • * If fT₄ <0.8 ng/dl in two determinations: initiate levothyroxine (4–6 μg/kg per day).

Results: N=337 (126 <27 WG). Exitus: 47 (12.4%). 38 (11%): No blood test was obtained. Patients with hypothyroxinaemia (normal TSH with fT₄ <0.8 ng/dl) n=11 (3%): 8 in the 1st blood test (range 0.41–0.79), three in the 2nd blood test (range 0.66–0.77 ng/dl), only one of 11 was treated with levothyroxine. • Patients treated: n=12 (3.5%): 8 for hyperthyrotropinemia (TSH mean 27.03, range 12.5–46.6 mU/l), three for hypothyroidism (TSH mean 41.3 mU/L, fT₄ mean 0.59 ng/dl) and one for hypothyroxinaemia (TSH 1.27 mU/l, fT₄ 0.41 ng/dl). Screening for congenital hypothyroidism (capillary TSH) was negative for all the patients. Seven patients are still on treatment.

Conclusion: Thyroid function of the preterm infants <30 WG should be evaluated, apart from universal screening for congenital hypothyroidism. The second week of life is an appropriate time to assess the thyroid function in preterm babies. The implementation of our protocol does not involve an excessive number of additional extractions. This protocol is able to detect which patients should be treated and wouldn’t be detected by capillary TSH.